Conventionally, as a method of precisely determining a sleep state or a sleep pattern including a depth of sleep of an object person, a polysomnography method of comprehensively measuring various waveforms in a variety of biological information such as brain waves, eyeball movement, muscle movement, or electrocardiographs is known. In this polysomnography method, the sleep depth representing a depth of sleep is determined by comprehensively distinguishing the waveforms in the measured biological information, and the sleep state is determined by analyzing the depth of sleep (for example, see Patent Literature 1).